1. Field of the Invention
The current invention relates generally to lifting of precast concrete elements and more particularly to the anchor or insert embedded into the concrete element as part of a hoisting assembly.
2. Description of the Prior Art
A hoisting assembly for lifting and tilting precast concrete blocks for construction is known in the art. Tilt-up construction has become a widely accepted economic method of producing and installing building elements. Frequently, concrete elements are created in a centralized location such as a prefabrication factory or precast yard and then transported to the building site. For purposes of transportation of the elements, hoisting assemblies are used. When these concrete elements are created on site or arrive on site, hoisting assemblies are use to reorient the elements and move them into place. Numerous patents relate to the hoisting assembly as a whole, such as U.S. Pat. No. 4,634,164 and U.S. Pat. No. 4,173,856 issued to Fricker. In such cases, anchors or inserts are cast into the concrete elements for engagement with a clutch of the hoisting assembly. The anchor disclosed in each of these patents is positioned below the edge surface of the precast concrete so that the concrete holds the anchor in place. The anchor has an exposed portion for engagement with the clutch. The anchor can simply extend above the precast concrete or can extend from an engagement recess formed in the precast element. Engagement recesses are generally formed by inserting a cap during the casting of the block, the cap being removed afterwards to define the recess. This engagement recess prevents bearing against the edge surface of the concrete. The anchor is intended to be permanently embedded in the concrete element, in most cases, with the end portion exposed within its recess.
While the anchor alone is cast into the concrete, bases are also used in conjunction with the anchors to further stabilize the anchor within the concrete. These bases or cages are generally plastic assemblies with legs. The plastic goes around the anchor and helps distribute forces such that the anchor is less likely to pull out of the concrete. Additionally, the insertion of a cross bar through a hole in the anchor embedded in the concrete is useful to further stabilize the anchor within the block. The base and the bar serve the purpose of rigidly retaining the anchor in the precast concrete element when embedded therein.
While all hoisting assemblies include an anchor and a clutch, hoisting assemblies can be divided into two categories based on their type of clutch. The first type of clutch is a "ring clutch". This clutch has a locking bolt or latch within a torus or donut-shaped ring. The bolt engages with an opening in one end of an anchor to connect the ring clutch to the anchor for hoisting the precast concrete element. The second type of clutch is a "bail lifter" where the clutch surrounds and contains the end of the anchor for lifting.
Examples of ring clutches and the anchors useful for engaging with such ring clutches to complete the hoisting assemblies are disclosed in U.S. Pat. No. 4,632,164 by Fricker, and U.S. Pat. No. 4,437,642 by Holt. Each of these hoisting assemblies includes a ring clutch with a moveable bolt for engaging a recess in an anchor.
Examples of hoisting assemblies with bail lifter variety clutches and the anchors useful in such hoisting assemblies include U.S. Pat. No. 4,700,979 by Courtois through its related Re. 33,881, and U.S. Pat. No. 4,671,554 issued to Lancelot. Each of these discloses a bail lifter with a socket in a coupler body for receiving and containing an anchor. As shown incidentally in these patents, anchors are known with ends in the shape of balls or nail-heads. Again, the bail lifter type clutch and the anchor together create the hoisting assembly.
As noted above, each type of clutch requires a specific type of anchor for interaction. The ring clutch variety requires an anchor type with an exposed hole for engagement with the bolt of the clutch. The bail lifter variety requires a wide head on the anchor to be contained within the clutch. These anchors are not interchangeable.
Different types of anchors and hoisting arrangements are chosen depending upon the type of precast concrete element or the lifting arrangement. For example, some elements are relatively thin, and some are created from lightweight concrete. Likewise, while some elements are lifted from an anchor in the face of the element, some are lifted from the edge. As the physical stresses on the concrete element differ in each case, a variety of hoisting assembly types are use. For each type of clutch used, a matching anchor is required.
In other cases where the type of hoisting assembly needed is not dictated by the parameters of the precast element, a limitation can arise due to a shortage of one type of hoisting clutch on the work site. For example, a job site where concrete elements are cast may have an adequate supply of anchors for use with ring clutches but not with bail lifters. If ring clutches are in short supply, additional anchors for engagement with the bail lifter must be ordered and delivered. There is always the possibility that this may cause delay, a serious problem for construction teams often resulting in large financial losses.
Similarly, a pre-cast yard receives specifications from the job site dictating that anchors be used that are compatible with the hoists on the job-site. Traditionally, pre-cast yards maintain a large inventory of anchors to accommodate these orders. The difficulty of the lack of interchangeability of anchors for the two clutch types results in inefficiencies. There is a need for one universal anchor that is adapted to be interchangeable between different types of clutches
Furthermore, anchors of the nail-head type are traditionally stamped out of pressed steel. Examples of manufacturers of such include anchors distributed by Richmond - Dayton Superior and Meadows Burke (the Ultra Lift system). While the incremental cost of each stamped anchor is relatively low, the capital investment in the equipment is extemely high. There is a need for a simpler and less capital intensive manufacturing process to create a malleable anchor.
It is an object and feature of the current invention to provide a universal anchor that can engage with more than one type of clutch of a hoisting assembly.
It is a further object of the invention to provide an anchor of malleable material that allows for ease and economies of manufacture.